Valve train for actuating gas exchange valves of an internal combustion engine

ABSTRACT

A valve train for actuating gas exchange valves of an internal combustion engine may include a first camshaft that is received such that it can be rotated in a first shaft axis, and a second camshaft that is received such that it can be rotated in a second shaft axis. At least one of the camshafts may be configured as an adjustable camshaft that comprises an outer shaft in which an inner shaft is received such that it can be rotated. At least one of the camshafts may be drive-connected via a drive means to a crankshaft of the internal combustion engine. A phase shifting member may be provided by way of which the phase position of at least one inner shaft can be changed relative to the phase position of at least one outer shaft of the camshaft. The phase shifting member may comprise an arrangement that is spaced apart from both shaft axes.”

The present invention relates to a valve train for actuating gas exchange valves of an internal combustion engine having a first camshaft which is received such that it can be rotated in a first shaft axis, and having a second camshaft which is received such that it can be rotated in a second shaft axis, at least one of the camshafts being configured as an adjustable camshaft and comprising an outer shaft, in which an inner shaft is received such that it can be rotated, at least one of the camshafts being drive-connected via a drive means to the crankshaft of the internal combustion engine, and a phase shifting member being provided, by means of which the phase position of at least one inner shaft can be changed relative to the phase position of at least one outer shaft of the camshaft.

PRIOR ART

DE 10 2006 049 243 A1 describes a valve train for actuating gas exchange valves of an internal combustion engine having a first camshaft and a second camshaft, and the camshafts are arranged parallel to one another and are configured as adjustable camshafts. Therefore, both camshafts have an outer shaft, in which in each case one inner shaft is received such that it can be rotated. Fixed cams are attached on the outer side of the outer shaft, which fixed cams are connected fixedly to the outer shaft so as to rotate with it, and, furthermore, adjustable cams are received on the outer shaft, which adjustable cams are connected fixedly to the inner shaft so as to rotate with it. If the phase position of the inner shaft is adjusted with respect to the phase position of the outer shaft, the adjustable cams rotate relative to the fixed cams, with the result that the control times, for example, of inlet valves and outlet valves can be changed with respect to one another.

The outer shafts of the adjustable camshafts are driven jointly via a drive means by way of a crankshaft of the internal combustion engine, with the result that the phase position of the two outer shafts with respect to one another cannot be changed. A phase shifting member is seated on one of the two camshafts on the end side, and the phase position of the inner shafts can be changed relative to the phase position of the outer shafts by way of the phase shifting member.

The structural complexity of a camshaft is increased considerably in a disadvantageous manner if a phase shifting member is arranged on an end side of the camshaft. The phase shifting members are usually actuated hydraulically, and fluid leadthroughs have to be produced as a result of the phase shifting member corotating with the rotational movement of the camshaft, which usually takes place via a plain bearing which adjoins the phase shifting member. Here, the load-bearing cross section of the outer shaft and/or the inner shaft is weakened by way of a plurality of oil ducts, and, in addition, a corresponding amount of installation space has to be provided for the arrangement of the phase shifting member on an end side of the camshaft. In particular, in the case of double overhead camshafts in the cylinder head of an internal combustion engine (what is known as DOHC), the installation space for the arrangement of a phase shifting member is frequently greatly restricted. As a result, it is desirable to simplify the structural and constructive complexity for forming a valve train, in particular configured as a DOHC valve train, and to configure it in a minimum manner in terms of installation space.

DISCLOSURE OF THE INVENTION

It is an object of the invention to develop a valve train having two camshafts for actuating gas exchange valves of an internal combustion engine, and the valve train is to comprise at least one adjustable camshaft and to take up as little installation space as possible. In particular, an improved constructive solution for arranging and actuating a phase shifting member is to be provided.

Proceeding from a valve train for actuating gas exchange valves of an internal combustion engine in accordance with the preamble of claim 1, said object is achieved in conjunction with the characterizing features. Advantageous developments of the invention are specified in the dependent claims.

The invention includes the technical teaching that the phase shifting member has an arrangement which is spaced apart from both shaft axes.

Here, the invention proceeds from the general concept of arranging the phase shifting member separately from the camshafts, and, in particular, the phase shifting member not being arranged directly on an inner shaft or on an outer shaft of one of the camshafts. Rather, the phase shifting member with its shifting axis is to be arranged in such a way that the shifting axis is arranged, for example, parallel to but spaced apart from both shaft axes. This results in the advantage that the phase shifting member can be loaded with a control fluid more simply, since the control fluid does not have to be routed through the inner shaft and/or the outer shaft and, in particular, no corresponding ducts have to be provided in the inner shaft and/or the outer shaft, with the result that said ducts also do not weaken the load-bearing material cross section. The invention solves the above problem, in particular, by virtue of the fact that the phase shifting member can be arranged freely; transmission means are merely to be provided, by way of which the phase shifting member can be coupled to at least one of the two camshafts.

For example, the phase shifting member can comprise a stator and a rotor, and the rotor can be rotated in the stator about the shifting axis by way of fluid loading. Here, the stator and the rotor can be arranged such that they can be rotated in a common shifting axis, the shifting axis being arranged spaced apart in parallel from the shaft axes of the camshafts. The rotor and/or the stator can intersect at least the outer shaft and/or the inner shaft of one of the camshafts, since the invention does not fundamentally claim that the phase shifting member is to be arranged in complete structural separation from the camshafts. Rather, the shifting axis is merely not to lie in one of the shaft axes of the camshafts.

The phase shifting member can particularly advantageously be operatively connected via a first transmission means to the at least one inner shaft. For example, the transmission means can be formed by way of a gearwheel pairing, it also being possible for the transmission means to be formed by way of a flexible drive means or the like.

The valve train can be configured with two adjustable camshafts, and the camshafts can comprise a respective outer shaft and a respective inner shaft, both inner shafts, in particular, being coupled to one another via the first transmission means such that their phase position with respect to one another cannot be changed. In particular, both inner shafts can be coupled to or via the phase shifting member.

The outer shaft of the first camshaft and the outer shaft of the second camshaft can further advantageously be capable of being driven jointly by the crankshaft of the internal combustion engine by way of the drive means. As a result, the two outer shafts of the camshafts rotate with an identical phase with respect to one another, and the two inner shafts are likewise coupled to one another via the first transmission means and rotate with an identical phase; the phase position of the two inner shafts can thus be changed via the phase shifting member relative to the phase position of the two outer shafts.

The first transmission means can be connected, for example, to the rotor of the phase shifting member, and the phase shifting member can be operatively connected via a second transmission means to the outer shaft of one of the camshafts. Here, the second transmission means can be connected to the stator of the phase shifting member. As a result, the phase position of a rotational movement which is transmitted via the first transmission means can be changed by way of an activation of the phase shifting member with respect to the rotational movement which is transmitted via the second transmission means. The particular advantage lies in the fact that the phase position of the two inner shafts of the camshafts can be changed relative to the phase position of the two outer shafts via the separately arranged phase shifting member.

It can also be provided according to one modified embodiment that the first transmission means is connected to the stator of the phase shifting member. Here, the second transmission means can also be connected to the rotor of the phase shifting member. The phase position of a rotational movement which is transmitted via the first transmission means can thus also be changed according to this variant by way of an activation of the phase shifting member with respect to the rotational movement which is transmitted via the second transmission means.

For example, the first transmission means between the inner shafts and the phase shifting member can be configured by means of a respective gearwheel pairing with a first gearwheel and a second gearwheel. Here, the first gearwheel can be connected rigidly, for example, to the rotor of the phase shifting member, and two further gearwheels can be provided which are seated on the respective inner shafts of the camshafts. As a result, the two gearwheels on the inner shafts engage at different circumferential positions into the gearwheel on the phase shifting member, with the result that the two inner shafts are connected to one another fixedly so as to rotate together and synchronously in terms of their phase position via the toothing system.

It is advantageous, furthermore, that the second transmission means between one of the outer shafts and the phase shifting member can be formed by means of a gearwheel pairing with a first gearwheel and with a second gearwheel. Here, for example, the first gearwheel can be connected to the stator of the phase shifting member, and the second gearwheel is seated on the outer shaft of one of the two camshafts. In particular, a further second gearwheel can also be seated on the further outer shaft, which further second gearwheel is likewise in engagement with the first gearwheel on the phase shifting member. It can be sufficient here that merely one outer shaft is driven by way of the crankshaft of the internal combustion engine via the drive means.

The shifting axis of the phase shifting member can form a triangular arrangement with the shaft axes of the camshafts. There is the possibility, furthermore, that the shifting axis lies in the same plane as the shaft axes of the camshafts. In the case of a triangular arrangement, however, the advantage can be utilized that the camshafts can be arranged at a smaller spacing from one another, without the diameter of the phase shifting member influencing the spacing of the two camshafts.

PREFERRED EXEMPLARY EMBODIMENT OF THE INVENTION

Further measures which improve the invention will be shown in greater detail in the following text together with the description of one preferred exemplary embodiment of the invention of the single FIGURE, in which:

the FIGURE shows a diagrammatic view of a valve train for actuating gas exchange valves of an internal combustion engine having two adjustable camshafts, constructed in accordance with the DOHC principle.

The figure shows a diagrammatic view of a valve train 1 for actuating gas exchange valves of an internal combustion engine having a first camshaft 10 which is received such that it can be rotated in a first shaft axis 11, and having a second camshaft 20 which is received such that it can be rotated in a second shaft axis 21. The two camshafts 10, 20 can be received jointly in a cylinder head of an internal combustion engine or in a cover module.

The exemplary embodiment shows the two camshafts 10 and 20 as adjustable camshafts, and the first camshaft 10 comprises an outer shaft 12 and an inner shaft 13, and the inner shaft 13 is mounted rotatably in the outer shaft 12. The second camshaft 20 comprises an outer shaft 22 and an inner shaft 23, the inner shaft 23 likewise being mounted rotatably in the outer shaft 22.

Fixed cams 14, 24 are attached on the two outer shafts 12, 22, which fixed cams 14, 24 are connected rigidly to the outer shafts 12, 22 so as to rotate with them. Furthermore, adjustable cams 15, 25 are received on the outer side of the outer shafts 12, 22 such that they can be rotated, which adjustable cams 15, 25 are connected fixedly to the inner shafts 13, 23 so as to rotate with them. If the phase position of the inner shafts 13, 23 is rotated with respect to the phase position of the outer shafts 12, 22, the adjustable cams 15, 25 rotate relative to the fixed cams 14, 24 about the shaft axes 11, 21.

The two outer shafts 12, 22 are driven jointly via a drive means 2, for example a chain or a toothed belt, and a drive wheel 4.1 is attached on the outer shaft 12 of the first adjustable camshaft 10, and a further drive wheel 4.2 is attached on the outer shaft 22 of the second adjustable camshaft 20. Here, the drive means 2 drives both outer shafts 12 and 22 jointly with an identical phase position to one another via the drive wheels 4.1 and 4.2. The drive takes place via a crankshaft 3 which is indicated merely diagrammatically.

A phase shifting member 30 is arranged between the two camshafts 10 and 20, and the phase shifting member 30 comprises a shifting axis 33 which is arranged spaced apart with respect to the first shaft axis 11 of the first camshaft 10 and with respect to the second shaft axis 21 of the second camshaft 20.

The phase shifting member 30 is connected via a first transmission means 34 to the inner shafts 13, 23 of the camshafts 10, 20, the outer shaft 22 of the second camshaft 20 being connected via a further, second transmission means 35 to the phase shifting member 30.

The first transmission means 34 is formed by way of a first gearwheel 34.1 which is connected to a rotor 32 of the phase shifting member 30. Furthermore, the first transmission means 34 comprises two second gearwheels 34.2, and the second gearwheels 34.2 are seated on the respective shaft axes 11 and 21 of the camshafts 10 and 20 and are connected to the inner shafts 13 and 23. The two inner shafts 13, 23 are connected rigidly to one another so as to rotate together by way of the engagement of the two second gearwheels 34.2 on the inner shafts 13, 23 with the first gearwheel 34.1.

The second transmission means 35 comprises a first gearwheel 35.1 which is connected to the stator 31 of the phase shifting member 30. Furthermore, the second transmission means 35 comprises a second gearwheel 35.2 which is connected to the outer shaft 22 of the second camshaft 20, the connection being shown merely by way of example, and it being possible for the second gearwheel 35.2 of the second transmission means 35 to be connected in an identical way to the outer shaft 12 of the first camshaft 10.

By way of an activation of the phase shifting member 30, the phase position of the inner shafts 13, 23 of the two camshafts 10, 20 can be changed with respect to the phase position of the outer shafts 12, 22, with the result that the phase position of the respective adjustable cams 15, 25 can be adjusted about the shaft axes 11, 21 relative to the fixed cams 14, 24. As a result, both adjustable camshafts 10, 20 can be adjusted by way of a separately arranged phase shifting member 30.

The exemplary embodiment shows a coupling of the first transmission means 34 to the rotor 32 of the phase shifter 30, a coupling to the stator 31 also being possible in the same way. Here, in a deviation from the illustration in conjunction with the stator 31, the second transmission means 35 can also be connected to the rotor 32.

The invention makes an activation of the phase shifting member 30 possible in a particularly simple way, since the accessibility to the phase shifting member 30 is simplified, in particular for fluid routing means. Furthermore, the camshafts 10, 20 comprise merely gearwheels 34.2 and 35.2 which are connected, for example, in one piece to the inner shaft 13, 23 and to the outer shaft 22. As a consequence, the result of the separate construction of the phase shifting member 30 in a divided manner from the camshafts 10, 20 is a simple construction of a valve train, it being possible for the valve train 1 to be of compact configuration, in particular, in the axial direction, that is to say in the structural extent along the shaft axes 11, 21. The limited installation space requirement is produced, in particular, by virtue of the fact that an installation space can be utilized for arranging the phase shifting member 30 which is situated between the two camshafts 10, 20.

The implementation of the invention is not restricted to the preferred exemplary embodiment which is specified in the above text. Rather, a number of variants are conceivable which use the illustrated solution, even in the case of embodiments of fundamentally different type. All the features and/or advantages which are apparent from the claims, the description or the drawings, including structural details or spatial arrangements, can be essential to the invention both per se and in a very wide variety of combinations. 

1.-11. (canceled)
 12. A valve train for actuating gas exchange valves of an internal combustion engine, the valve train comprising: a first camshaft received such that the first camshaft is rotatable in a first shaft axis; a second camshaft received such that the second camshaft is rotatable in a second shaft axis, wherein at least one of the first camshaft or the second camshaft is configured as an adjustable camshaft and comprises an outer shaft in which an inner shaft is rotatably received, wherein at least one of the first camshaft or the second camshaft is drive-connected via a drive means to a crankshaft of the internal combustion engine; and a phase shifting member by way of which a phase position of the inner shaft is changeable relative to a phase position of the outer shaft, wherein the phase shifting member includes an arrangement spaced apart from the first and second shaft axes.
 13. The valve train of claim 12 wherein the phase shifting member comprises a stator and a rotor, wherein the stator and the rotor are rotatable in a common shifting axis, the common shifting axis being spaced apart from and parallel to the first and second shaft axes.
 14. The valve train of claim 13 wherein the phase shifting member is operatively connected via a first transmission means to the inner shaft, wherein the first transmission means is connected to the rotor of the phase shifting motor.
 15. The valve train of claim 12 wherein the phase shifting member is operatively connected via a first transmission means to the inner shaft.
 16. The valve train of claim 15 wherein the phase shifting member is operatively connected via a second transmission means to the outer shaft of one of the first camshaft or the second camshaft.
 17. The valve train of claim 16 wherein the second transmission means is connected to a stator of the phase shifting member.
 18. The valve train of claim 16 wherein the phase shifting member comprises a stator and a rotor, wherein the stator and the rotor are rotatable in a common shifting axis, the common shifting axis being spaced apart from and parallel to the first and second shaft axes, wherein the second transmission means is connected to the stator of the phase shifting member.
 19. The valve train of claim 18 wherein the second transmission means between the outer shaft of one of the first camshaft or the second camshaft and the phase shifting member is configured as a gearwheel pairing with a first gearwheel and a second gearwheel.
 20. The valve train of claim 12 wherein the first camshaft is configured as the adjustable camshaft and comprises the outer shaft in which the inner shaft is rotatably received, wherein the second camshaft is configured as an adjustable camshaft and comprises an outer shaft and an inner shaft, wherein a first transmission means couples the inner shaft of the first camshaft to the inner shaft of the second camshaft such that the phase position of the inner shaft of the first camshaft cannot be changed relative to a phase position of the inner shaft of the second camshaft.
 21. The valve train of claim 20 wherein the outer shafts of the first and second camshafts can be driven jointly by the crankshaft of the internal combustion engine by way of the drive means.
 22. The valve train of claim 20 wherein the first transmission means between the inner shafts and the phase shifting member is configured as respective gearwheel pairings with a first gearwheel and with a second gearwheel.
 23. The valve train of claim 12 wherein the phase shifting member comprises a stator and a rotor, wherein the stator and the rotor are rotatable in a common shifting axis, the common shifting axis being spaced apart from and parallel to the first and second shaft axes, wherein the common shifting axis forms a triangular arrangement with the first and second shaft axes. 